libpulseaudio: preserve vapi files
libpulseaudio: preserve vapi files

The current postInstall removes all of $out/share, which also includes pulse's
vapi/deps files. Certain projects (budgie-desktop, for example) require these
definitions, but do not require the full pulseaudio server. Preserving these
files allows these projects to only depend on libpulseaudio.

Fixes #73463.

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs